This invention relates to test apparatus and method for determining the asbestos fiber release potential of asbestos-containing compositions.
Asbestos has long been recognized as a material which has excellent fire-retardant properties. For many years it was used in building construction where fire-retardant construction was desired. More recently environmental concerns relative to the human health implications of asbestos have been expressed. One of the concerns involves the inhalation of airborne asbestos fibers and their resultant accumulation in the lungs. One present belief is that above a certain threshold level of exposure to a population there exists a correlation of the incidence of health problems including certain cancers to the amount of asbestos accumulation. Due to the rather extensive and widespread usage of asbestos as a fire-retardant material in building construction over a number of years, there presently exist environmental situations where appreciable numbers of individuals come within the vicinity of asbestos-containing materials. The mere existence of asbestos-containing material in an environment does not of itself create a health problem. Rather, concern arises about release of asbestos fibers from a material such that they become airborne and hence susceptible to being inhaled by individuals who are present in the immediate environment. Whether an existing building containing asbestos fire-retardant materials in fact poses a potential asbestos exposure problem which could have health implications has heretofore not been determinable on any reliable scientific basis. The only documental test procedure of which applicant is aware is ASTM E736-80 involving Cohesion/Adhesion of Sprayed Fire-Resistive Materials Applied to Structural Members, and that is not addressed to the matter of asbestos fiber release potential.
The present invention is directed to test apparatus and method which can provide a meaningful indication as to the fiber release potential of asbestos-containing materials.
One commonly used technique for fire-guarding structural elements of a building involved the creation of a fire-retardant composition containing a percentage of asbestos. In general the compositions which were in fact used in the field were prepared by contractors on site without particular concern for the relative proportion of asbestos in the compositions. For example the compositions were often prepared by mixing asbestos into a carrier which was subsequently sprayed onto the structural building elements. The sprayed-on fire-guarding composition cured into an overlying layer somewhat like a plaster composition. In any given installation the asbestos content could range over a wide percentage; for example a range of ten to fifty percent was not atypical. With aging and use the asbestos-containing fire-resistive compositions in a building may crumble, disintegrate or otherwise come into a state of disrepair. Such conditions can give rise to the release of asbestos fibers to the air and such aiborne fibers may well remain within the building so that occupants are exposed to them.
Often the fire-guarded elements were the structural members of the building such as the steel beams. While steel will obviously not combust, the reason for fire-guarding is to prevent the beams from buckling, sagging and leading to ultimate collapse of the building structure in the event of fire. The only way to determine the potential for release of asbestos fibers in a given building is by means of in situ testing. Insofar as applicant is aware there has heretofore been no procedure suggested for accomplishing this, much less accomplishing it in a manner which is reasonably indicative of the fiber release potential.
One of the complicating factors in attempting such in situ testing is that the structural building elements such as the beams are often in locations which are accessible only with difficulty. For example a beam may be located above a drop ceiling and it is necessary to obtain access through the ceiling to get to the beam. Due to the design of many buildings these spaces between the beams and other partitioning structures such as the drop ceiling are designed as plenums for ventilation purposes and hence they are subject to varying degrees of air flow. In order to accomplish an in situ testing procedure where airborne release of fibers is to be measured it is necessary that a reliable testing procedure address the problem of varying air flow in the vicinity where testing is to be done. With the invention variable airflow will not complicate or confound measurements.
The present invention is directed to test apparatus and method for determining in situ the release potential of asbestos fibers and is particularly well suited for use in buildings where the asbestos-fiber-containing composition has been previously applied to structural elements within the building such as described above. The invention provides a test procedure for the asbestos fiber release potential for various compositions and at various sites so that meaningful indicators of release potentials can be obtained. Furthermore the invention may be practiced in locations where in situ testing procedure is encumbered by various disturbing factors such as described above.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.